I think what you said is very close. The actual syntax of the calculated fields would probably be something like:
IF [Message_Type]=0 THEN rtime END
IF [Message_Type]=0 THEN page_hits END
These would both be calculated at the row level and you would end up with two new measures. These measures can then be aggregated as desired (e.g. AVG and COUNT)
Thanks Joshua! That was perfect.
for response time it looked like this. I ended up using a different field and then changes it from milliseconds to seconds.
IF [MESSAGE_TYPE]=0 THEN [PAGE_LOAD_TIME] END *.001
You're welcome! Glad to help!